Content addressable memory (CAM) and method of downloading and banking filters

Abstract

A Content Addressable Memory (CAM) that downloads and banks a group of filters. Each filter has an associated filter-index, which is mapped in a mapping table to an available CAM address for storing the associated filter. Each succeeding filter in the group of filters is stored in a higher address in the CAM. The plurality of CAM addresses may not all be contiguous, in which case the mapping table maps each succeeding filter-index to the next higher available CAM address without regard to contiguity of the addresses.

1. A Content Addressable Memory (CAM), comprising:
 means for downloading a group of filters, each of said filters having an associated filter-index; 
 a plurality of CAM addresses for storing the group of downloaded filters; and 
 a mapping table for mapping each filter-index to an associated CAM address available for storing the downloaded filter associated with the filter-index, wherein each succeeding filter in the group of filters is stored in a higher address in the CAM. 
 
     
     
       2. The CAM of  claim 1 , wherein the plurality of CAM addresses are not all contiguous, and the mapping table maps each succeeding filter-index to the next higher available CAM address without regard to contiguity of the addresses. 
     
     
       3. The CAM of  claim 2 , wherein a portion of the CAM addresses that are not available are reserved for possible downloading of an additional group of filters. 
     
     
       4. The CAM of  claim 3 , wherein the groups of filters are of different sizes, and the number of reserved CAM addresses is equal to the number of filters in a largest group. 
     
     
       5. The CAM of  claim 1 , further comprising a second mapping table for mapping each CAM address back to the associated filter-index. 
     
     
       6. The CAM of  claim 1 , wherein a plurality of filter-groups are downloaded to the CAM, and the CAM comprises a plurality of mapping tables, one mapping table for each filter-group, wherein each mapping table maps each filter-index in the table's filter-group to an associated CAM address available for storing the downloaded filter associated with the filter-index. 
     
     
       7. In a Content Addressable Memory (CAM), a method of downloading and banking in the CAM, a filter-group having a plurality of filters, said method comprising:
 establishing a mapping table for the filter-group; 
 downloading a plurality of filter-indexes associated with the filters in the filter-group; and 
 mapping each filter-index to an associated CAM address available for storing the downloaded filter associated with the filter-index, wherein each succeeding filter in the group of filters is stored in a higher address in the CAM. 
 
     
     
       8. The method of  claim 7 , wherein the plurality of CAM addresses are not all contiguous, and the step of mapping includes mapping each succeeding filter-index to the next higher available CAM address without regard to contiguity of the addresses. 
     
     
       9. The method of  claim 8 , further comprising reserving a portion of the CAM addresses for possible downloading of an additional group of filters. 
     
     
       10. The method of  claim 9 , wherein the groups of filters are of different sizes, and the step of reserving a portion of the CAM addresses includes reserving a number of CAM addresses equal to the number of filters in a largest group. 
     
     
       11. The method of  claim 7 , further comprising establishing a second mapping table for mapping each CAM address back to the associated filter-index. 
     
     
       12. The method of  claim 7 , further comprising:
 downloading a plurality of filter-groups to the CAM; 
 establishing a mapping table for each of the plurality of filter-groups; and 
 mapping by each mapping table, each filter-index in the table's filter-group to an associated CAM address available for storing the downloaded filter associated with the filter-index. 
 
     
     
       13. In a Content Addressable Memory (CAM), a method of downloading and banking in the CAM, a filter-group having a plurality of filters, said method comprising:
 a) downloading a plurality of filter-indexes associated with the filters in the filter-group; 
 b) establishing a mapping table for mapping each filter-index to an associated CAM address available for storing the downloaded filter associated with the filter-index; 
 c) determining the lowest available filter CAM address; 
 d) associating the first filter-index with the lowest available filter CAM address; 
 e) determining the next higher available filter CAM address; 
 f) associating the next filter-index with the next higher available filter CAM address; 
 g) determining whether the last filter-index in the downloaded group has been associated with an address; 
 h) upon determining that the last filter-index in the downloaded group has not been associated with an address, repeating steps e) through g); and 
 i) upon determining that the last filter-index in the downloaded group has been associated with an address, ending the method. 
 
     
     
       14. The method of  claim 13 , wherein step e) includes determining a CAM address that is not contiguous to a previously associated CAM address.